Pollutant Information: Sulphur Dioxide 

About Sulphur Dioxide

Category: Air pollutants

Sulphur dioxide (SO2 expressed as SOx) has long been recognized as a pollutant because of its role, along with particulate matter, in forming winter-time smog. Studies indicate that SO2 causes nerve stimulation in the lining of the nose and throat. This can cause irritation, coughing and a feeling of chest tightness, which may cause the airways to narrow. People suffering from asthma are considered to be particularly sensitive to SO2 concentrations. Fuel combustion accounted for 93% of UK SO2 emissions in 2016 with the main sources being the combustion of coal, heavy fuel oil and petroleum coke (a solid fuel produced in crude oil refineries).  Sulphur dioxide emissions from fuel combustion originate from the sulphur contained in the fuel being burnt, and coal, coal-based smokeless fuels, fuel oil and petroleum coke all have a high sulphur content relative to other fuels.  

Since 1990, SO2 emissions have declined by 95%.  This has occurred due to a steady decline in the use of coal and fuel oil in all sectors of the UK economy, plus improved abatement technology, most notably the fitting of flue-gas desulphurisation (FGD) systems at coal-fired power stations.  Across all sources, emissions from use of coal have reduced by 98% between 1990 and 2016, while for fuel oil the figure is 97%.  Emissions from the use of coal to generate electricity have decreased by 99% since 1990, and emissions in 2016 were down 63% from the previous year due to closure of sites and reduced coal consumption at the remainder.  Fuel oil is no longer used in significant quantities at power stations and emissions in 2016 were just 0.2% of the emission in 1990.  In recent years, as the consumption of coal and fuel oil in the UK has dwindled, the percentage contribution of petroleum coke to the UK inventory has increased.  Emissions from the use of petroleum coke were just 1% of the UK total in 1990 but grew to 26% by 2016, while for coal the corresponding figures are 71% of emissions in 1990 and 34% in 2016 and for fuel oil, the figures are 19% in 1990 and 10% in 2016.  Petroleum coke formed in UK refinery processes is burnt to recover energy while imported petroleum coke is used as a fuel for certain industrial processes and as a residential sector fuel, for example in smokeless fuels.

More stringent legislation on the sulphur content of liquid fuels used in transportation has also helped to reduce emissions, and emissions from gas oil and road diesel have decreased by 91% since 1990.

Emissions in 2016 are 43% below the UK's National Emission Ceilings Directive and Gothenburg Protocol targets for 2020.

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Time series graph


Notable events

Start year End year Sector Information Impact
1985 2009 Combustion in Energy and Transformation Industry Power Station Flue Gas Desulphurisation (FGD) abatement equipment installed. By 2008 FGD contributed between 1/4 and 1/3 of total emissions reductions from power stations. Decrease in emissions
1984 1985 Combustion in Industry/Residential/Commercial 1984 miners' strike led to a significant decrease in the use of coal for combustion in electricity generation. A noticeable dip in emissions from coal-fired combustion sources in 1984 but increase in use of alternative fuels (e.g. Oil) and resulting emissions of pollutants (Cadmium & Lead). Decrease in emissions
1981 2014 Combustion in Industry/Residential/Commercial Restriction on use of smoke producing fuels in urban areas, switch from coal and oil to natural gas and from 2006 reduction in sulphur content of gas oil Decrease in emissions
2009 2012 Public Electricity and Heat Production The economic downturn has caused significant reductions in energy demands and many industries have made cut backs or closures, resulting in reduced emissions. Decrease in emissions
2010 2012 Public Electricity and Heat Production As a result of the economic downturn the drive to cut energy costs has resulted in an increase in solid fuel use, particularly in 2012 some coal-sensitive pollutants have seen a significant rise in coal burning emissions. Increase in emissions
2012 2015 Combustion in energy and transformation industry Coal combustion in power stations has fallen by over 40% Decrease in emissions